AJC P1 Q8 (a)

AJC P1 Q8 (a)

Prelims

Let \({{u}_{n}}=\ln \left( \frac{n}{n+1} \right)+\frac{1}{n+1}-\frac{1}{n}\) ,

  1. Find in terms of \(N\), an expression for \({{S}_{N}}\), where \({{S}_{N}}={{u}_{1}}+{{u}_{2}}+...+{{u}_{N}}\), simplifying your result as far as possible.
  2. Show that \({{S}_{N}}<0\) for all \(N\ge 1\).

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Answer:\(S_N = -\ln(N+1) + \frac{1}{N+1} - 1\); \(S_N < 0\)

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